realFFT function
Implementation
List<Complex> realFFT(List<double> data) {
var real = data.toList();
var imag = List<double>.filled(data.length, 0);
transform(real, imag);
List<Complex> res = [];
for (int i = 0; i < real.length; i++) {
res.add(Complex.ri(real[i], imag[i]));
}
return res;
}